HE studies measure the quality of any work based on research, logic and execution.
Execution being how well anything is written and argued.
Logic being the quality of the argument and whether it is understandable.
Research being the quality of the bibliography and how well it is used.
Here are some more specific recommendations on how to 'fill' your bibliography:
Ensure you use any texts mentioned in the assessment question.
If a 'Reading List' of PDF's is provided in the Moodle page for the subject, be sure to use these. It is an easy to access collection of quality sources - but how you use them will depend on your understanding, whether they are generally relevant to the essay topic and whether they are specifically relevant to the trajectory of your essay's argument.
Now consider point 3 to 8 - "How to fill your Bibliography":
The bibliography included in the Subject outline document (usually at the end) lists quality sources that are recommended for consultation.
The Subject outline document also includes online journals recommendations that are useful for consultation. These journals (and similar) range in academic reputation from publications for professionals to the higher level research journal.
The Ebsco online journals resource is an accessible academic journal database that should be a priority resource for consultation when researching for any postgraduate essay. (The subject outline document has instructions for how to get login credentials for Ebsco. Induction and Study Skills has instruction on best practise usage and how to access it).
The work of Seminal authors in the field of research you are studying.
Seminal books in the particular field of research you are studying (monographs).
Online web resource that are relevant and of suitable quality.
Finally, do not include any item in your bibliography that you do not directly quote or reference in your essay - 'padding' one's bibliography is not acceptable.